i dont think so we can change the database name once it is created but the only think we can do is change the dbname if it is a part of domain by this command
alter database db-name global rename to domainname.db-name ;
correct me if i am wrong
1)alter database backup controlfile to trace;
2)edit that trace file replacing "reuse" with "set" as well as
"noresetlogs" to resetlogs"...of course make sure your new dbname is changed.
3)chg ur init.ora
4)remove the "recover database ..." in the trace file then run it!